Documentation on Cycles BVH traversal and intersection algorithm
The wiki page for Cycles' BVH links to three publications that it implements. Below you can find the links to the papers* as well as the abstracts.

(*) The links are different from the ones in the wiki, because one of them returns a 404 and another one is very slow.

Stich, Martin, Heiko Friedrich, and Andreas Dietrich. "Spatial splits
   in bounding volume hierarchies." Proceedings of the Conference on
   High Performance Graphics 2009. ACM, 2009.


  Bounding volume hierarchies (BVH) have become a widely used
  alternative to kD-trees as the acceleration structure of choice in
  modern ray tracing systems. However, BVHs adapt poorly to nonuniformly
  tessellated scenes, which leads to increased ray shooting costs. This
  paper presents a novel and practical BVH construction algorithm, which
  addresses the issue by utilizing spatial splitting similar to
  kD-trees. In contrast to previous preprocessing approaches, our method
  uses the surface area heuristic to control primitive splitting during
  tree construction. We show that our algorithm produces significantly
  more efficient hierarchies than other techniques. In addition, user
  parameters that directly influence splitting are eliminated, making
  the algorithm easily controllable.




Wald, Ingo, Solomon Boulos, and Peter Shirley. "Ray tracing deformable scenes using dynamic bounding volume hierarchies." ACM Transactions on Graphics (TOG) 26.1 (2007): 6.


  The most significant deficiency of most of today’s interactive ray
  tracers is that they are restricted to static walkthroughs. This
  restriction is due to the static nature of the acceleration structures
  used. While the best reported frame-rates for static geometric models
  have been achieved using carefully constructed kd-trees, this paper
  shows that bounding volume hierarchies (BVHs) can be used to
  efficiently ray trace large static models. More importantly, the BVH
  can be used to ray trace deformable models (sets of triangles whose
  positions change over time) with little loss of performance. A variety
  of efficiency techniques are used to achieve this performance, but
  three algorithmic changes to the typical BVH algorithm are mainly
  responsible. First, the BVH is built using a variant of the “surface
  area heuristic” conventionally used to build kd-trees. Second, the
  topology of the BVH is not changed over time so that only the bounding
  volumes need be re-fit from frame to frame. Third, and most
  importantly, packets of rays are traced together through the BVH using
  a novel integrated packet-frustum traversal scheme. This traversal
  scheme elegantly combines the advantages of both packet traversal and
  frustum traversal, and allows for rapid hierarchy descent for packets
  that hit bounding volumes, as well as rapid exits for packets that
  miss. A BVH-based ray tracing system using these techniques is shown
  to achieve performance for deformable models comparable to that
  previously available only for static models.




Dammertz, Holger, Johannes Hanika, and Alexander Keller. "Shallow bounding volume hierarchies for fast SIMD ray tracing of incoherent rays." Computer Graphics Forum. Vol. 27. No. 4. Oxford, UK: Blackwell Publishing Ltd, 2008.


  Photorealistic image synthesis is a computationally demanding task
  that relies on ray tracing for the evaluation of integrals. Rendering
  time is dominated by tracing long paths that are very incoherent by
  construction. We therefore investigate the use of SIMD instructions to
  accelerate incoherent rays. SIMD is used in the hierarchy
  construction, the tree traversal and the leaf intersection. This is
  achieved by increasing the arity of acceleration structures, which
  also reduces memory requirements. We show that the resulting
  hierarchies can be built quickly and are smaller than acceleration
  structures known so far while at the same time outperforming them for
  incoherent rays. Our new acceleration structure speeds up ray tracing
  by a factor of 1.6 to 2.0 compared to a highly optimized bounding
  interval hierarchy implementation, and 1.3 to 1.6 compared to an
  efficient kd-tree. At the same time, the memory requirements are
  reduced by 10–50%. Additionally we show how a caching mechanism in
  conjunction with this memory efficient hierarchy can be used to speed
  up shadow rays in a global illumination algorithm without increasing
  the memory footprint. This optimization decreased the number of
  traversal steps up to 50%.